Ultrasound lens structure cleaner architecture and method using standing and traveling waves

ABSTRACT

A lens structure system with a lens structure and a multi-segmented transducer coupled to the lens structure. Each segment in the plurality of segments has a first conductor and a second conductor, wherein the first conductor and the second conductor are electrically coupled to the segment. The system also has circuitry for applying a voltage to selected segments in the plurality of segments with standing wave signals and traveling wave signals.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/064,645 filed on Oct. 7, 2020, which is also a continuation of U.S.patent application Ser. No. 15/395,665, filed on Dec. 30, 2016 (now U.S.Pat. No. 10,838,199 issued on Nov. 17, 2020), the contents of which areherein incorporated by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

The preferred embodiments relate to various systems where debris orcontaminants are to be removed from lens-related apparatus in thesystem, and more particularly to an ultrasound architecture and methodin such a system.

A lens structure as used in this document is intended to include a lens,lens cover, or other surface through which a signal (e.g., light) maypass, and where the apparatus is exposed to potential contaminants thatmay reduce the likelihood of successful signal passage through theapparatus. As one prominent example, in the automotive industry, camerasare assuming an important role in both Driver-Assisted Systems (DAS) andautomatic safety systems. This technology commonly first appeared inrelatively expensive vehicles and has migrated to less expensive ones.Indeed, the National Highway Traffic Safety Administration (NHTSA) hasmandated that all new cars must be outfitted with rear view cameras by2018. Cameras are also now being incorporated into side view mirrors toassist drivers with lane changes and currently under consideration by atleast one automobile manufacturer is the possible replacement of vehicleside view mirrors with side view cameras. Besides alleviating blindspots for the driver, front cameras integrated into the windshieldprovide Forward Collision Warning (FCW), Following Distance Indication(FDI), and Lane Departure Warnings (LDW). Of course, lens structuresalso may be used in other implementations, including, for example,outdoor surveillance cameras and lighting systems.

In the above context and others, and as the trend toward additional lensstructures increase or become more ubiquitous, keeping the lensstructure (e.g., lenses and lens covers) free of contaminants becomes amore prevalent need and is particularly important in safety-relatedapplications. Further, the location, accessibility, or the user interestmay prove inconvenient for manual cleaning of the lens, so thatautomated approaches may be desirable. As one prior art approach to thisissue, several manufacturers have considered a miniature spray and wipersystem. This design, however, requires (1) a small pump and nozzle; (2)a motorized wiper assembly; and (3) a running a hose from a fluid tankto the location of the nozzle, which may necessitate a run from thevehicle front where a fluid tank is typically located, to the vehicleback, at least for the rear view camera, which is typically located atthe rear of the vehicle. As a result, this design is mechanicallycomplex and potentially expensive.

Given the preceding, the present inventors seek to improve upon theprior art, as further detailed below.

BRIEF SUMMARY OF THE INVENTION

In a preferred embodiment, there is a lens structure system. The systemcomprises a lens structure and a multi-segmented transducer coupled tothe lens structure. Each segment in the plurality of segments comprisesa first conductor and a second conductor, wherein the first conductorand the second conductor are electrically coupled to the segment. Thesystem also comprises circuitry for applying a voltage to selectedsegments in the plurality of segments, wherein the circuitry forapplying a voltage comprises circuitry for applying a voltage withstanding wave signals and circuitry for applying a voltage withtraveling wave signals.

Numerous other inventive aspects are also disclosed and claimed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1A illustrates a preferred embodiment system in a perspectiveexploded view.

FIG. 1B illustrates a top view of the ultrasonic transducer of FIG. 1A.

FIG. 1C illustrates the lens cover affixed atop the upper annularsurface of an ultrasonic transducer.

FIGS. 2A and 3A illustrate perspective views, and FIGS. 2B and 3Billustrate side views, of a membrane MEM and its mode shape diagrams ofa first mode (0,1) shape.

FIGS. 4A and 5A illustrate perspective views, and FIGS. 4B and 5Billustrate side views, of a membrane MEM and its mode shape diagrams ofa second mode (1,1) shape.

FIG. 6 illustrates a top view of the two separate oscillating regionsOR₁ and OR₂, about line DL₁, as achieved in FIGS. 4A and 4B.

FIGS. 7A and 8A illustrate perspective views, and FIGS. 7B and 8Billustrate top views, of a mode (2,1) shape.

FIG. 9 illustrates a preferred embodiment transducer and biasingconductors connected thereto.

FIG. 10 illustrates an example mechanical traveling wave graphimplementing a (1,1) mode.

FIGS. 11 through 14 illustrate top views of example positions of thewave of FIG. 10 .

FIG. 15 illustrates biasing signals to achieve a traveling wave (1,1)mode.

FIG. 16 illustrates using opposing polling areas and biasing signals toachieve a traveling wave (1,1) mode.

FIG. 17 illustrates a preferred embodiment method of operating thesystem of FIGS. 1A through 1C.

FIG. 18 illustrates a schematic of an ultrasonic lens cleaning systemincluding a four-segment transducer arrangement and a driver IC toprovide phase transducer signals to generate either or both a standingand traveling wave to a lens.

FIG. 19 illustrates a preferred embodiment vehicle V with multipleimplementations of the system of FIGS. 1A through 1C.

DETAILED DESCRIPTION OF EMBODIMENTS

FIGS. 1A through 1C illustrate various views of a lens structurecleaning system 10 according to a preferred embodiment. FIG. 1Aillustrates system 10 in a perspective exploded view, thereby separatelyillustrating a lens cover 12 that is to be coupled to an ultrasonictransducer 14, that is, affixed in some manner (e.g., atop an upperannular surface, directly, or indirectly through an additionalmember(s)) of ultrasonic transducer 14 so that vibrations fromultrasonic transducer 14 may be transmitted either directly, orindirectly via any intermediate apparatus, to lens cover 12. FIG. 1Billustrates a top view of just ultrasonic transducer 14, and FIG. 1Cillustrates lens cover 12 once affixed atop the upper annular surface ofan ultrasonic transducer 14, as may be achieved via various adhesivesthat may be selected by one skilled in the art. Various aspects ofsystem 10 are further described below, with reference to all three ofthese figures, and additional features may be included in connectionwith system 10 (e.g., seals, housings, and the like), but such featuresare not described so as to focus the discussion on preferred embodimentaspects.

Lens cover 12 is intended to represent any type of lens structure as wasintroduced in the Background of The Invention section of this document.In the example of system 10, lens cover 12 is a disc with a transparentcenter section 12 _(SC) (shown with a contrasting shading fordistinction to the remainder) and an outer annular ring 12 _(AR) thatsurrounds transparent center section 12 _(SC). Thus, in general light inthe visible spectrum may readily pass through transparent center section12 _(SC), while it is otherwise blocked by outer annular ring 12 _(AR).In this manner, a preferred embodiment also may include a camera CM, andits respective lens, placed proximate to lens cover 12, wherebygenerally light may pass through transparent center section 12 _(SC) soas to reach the camera lens, but the lens is otherwise protected by theadditional surface provided by lens cover 12. In many environments,transparent center section 12 _(SC) may become occluded by the presenceof additional contaminating matter (e.g., dirt, water, other airborneconstituents) so that light is partially or fully blocked from passingthrough that section, and the preferred embodiments endeavor to reduceor dispel such matter from the surface of lens cover 12.

Transducer 14, in a preferred embodiment, is formed from a cross-sectionof a cylindrical piezoelectric material, and preferably it has an outerdiameter smaller than the outer diameter of lens cover 12. By way ofexample, therefore, the outer diameter of transducer 14 may be 10 to 30mm, while the larger outer diameter of lens cover 12 may be 12 to 35 mm.Thus, once assembled (e.g., FIG. 1C), the outer perimeter of lens cover12 extends in some margin beyond the outer diameter of transducer 14. Asappreciated below, such a configuration may improve the effectiveness ofstanding and traveling waves transmitted from transducer 14 to lenscover 12, thereby improving the ability to dispel contaminants from thesurface of that lens cover. Transducer 14 is a segmented transducer, asdefined by having plural circular sectors, each having a pair ofconductors so as to apply a voltage to the sector. In the exampleillustrated, transducer 14 has four such segments (or sectors), shown inFIG. 1B as S₁, S₂, S₃, and S₄, each consisting of approximately, orslightly less than, 90 degrees of the entire 360 degree circularcross-sectional perimeter of the transducer. Each segment S_(x) has anouter electrode SOE_(x) and an inner electrode SIE_(x), as may beachieved by silk-screening or otherwise attaching a thin conductivematerial to the respective outer and inner diameter of the piezoelectricmaterial. As shown in a later FIG. 9 , a preferred embodiment mayinclude electrical connectors/wires connected to each of the illustratedelectrodes, and a driver circuit for outputting signals to theconductors, whereby such signals are therefore applied, and alternatedin amplitude, sign, and frequency, so as to achieve various preferredembodiment aspects further described below.

Given the preferred embodiment apparatus described above, transducer 14may be excited with various signals so as to communicate vibrationalforces into the abutted lens cover 12. Such waves may be communicated inthree different vibration modes, namely, radial mode at low frequencies(e.g., 44 kHz) and which are along the radii of the circular crosssection of transducer 14, axial mode at relative middle frequencies(e.g., 250 kHz), which are in the direction of the axis of thecylindrical transducer (i.e., vertical in FIGS. 1A-1C), and a wall modeat higher frequencies (e.g., 2 MHz), which are modes that represent theradial motion of the wall thickness with respect to the outer wall oftransducer 14. In a preferred embodiment, axial mode vibrations arepreferred, as they are likely to cause vibrations that are tangentialfrom the surface of lens cover 12, thereby providing a greaterlikelihood of dislodging certain contaminants (e.g., dust, water) fromthat surface. Note that frequency ranges of the various mode types mayoverlap. For example, high order radial modal frequencies will overlapwith the axial modal frequencies, and high order axial modal frequencieswill overlap with wall modal frequencies. However, in practice, this isnot normally an issue because as mode orders increase, so does the modaldamping.

Further to the preceding, also in the preferred embodiment, thevibrational forces are applied at excitation amplitudes and frequenciesso as to transmit both standing and traveling waves, either insequential or concurrent fashion, into the desirably chosen circularmembrane shape of the abutted lens cover 12. Thus, each type of wave isfurther detailed below, first with a discussion of standing waves andsecond with a discussion of traveling waves, with each applied to lensstructure cleaning system 10.

As is known in certain areas of physics, a standing wave is a stationaryvibrational pattern created within a medium when two waves of the samefrequency propagate through the medium in opposite directions. As aresult, regions of minimum displacement (e.g., nodes) and regions ofmaximum displacement (e.g., anti-nodes) are created at fixed locationsin the medium. As a result, the waves cause displacement along themedium (i.e., lens cover 12 in this instance), yet at the physicallocations where wave interference occurs, there is little or nomovement. Hence, in a circular membrane as exists in the preferredembodiment, where standing waves are so transmitted, the art definescertain mode shapes of the vibrational tendencies and movements of thesurface being vibrated. Each mode shape is identified in the art by aconvention of mode (d,c) shape, where d is the number of nodal diametersacross the membrane surface, and c is the number of nodal circles at orwithin the perimeter of the circular membrane, where the term nodal (ornode) refers to a point, line, or circle on the structure that has zeroamplitude vibration, that is, it does not move, while the rest of thestructure is vibrating. Various examples of mode shapes, by way ofintroduction and also in connection with preferred embodiments, arefurther explored below.

To further introduce mode shapes and various preferred embodimentaspects, FIGS. 2A and 3A illustrate perspective views, and FIGS. 2B and3B illustrate side views, of a membrane MEM and its mode shape diagramsof a first mode (0,1) shape in a standing wave excitation that may beachieved by applying a voltage to the multiple-segmented transducer 14of the preferred embodiment as if it were a single segmented transducer;such an effect may be achieved, therefore, by applying a first sine wavepotential to all of its outer electrodes and a second sine wavepotential, 180 degrees offset from the first sine wave (also achievableby 180 degree apart cosine potentials, instead of sine), to all of itsinner electrodes, where both sine waves have a same first modalfrequency. Alternatively, the effect may be achieved by applying a sinewave potential to all of the outer electrodes while connecting the innerelectrodes to ground (or, vice versa, that is, grounding the outerelectrodes and connecting the same sine wave to all inner electrodes). Amodal frequency is one of the resonant frequencies for the system underconsideration (i.e., here, lens cover 12), where the particular resonantfrequency, among multiple resonant frequencies of the system, causes theshape of the respective mode. In this regard, FIGS. 2A, 2B, 3A, and 3B,therefore, represent an instance where transducer 14 receives a voltageand first modal frequency, f_(m(0,1)), which creates mode (0,1) shape,also known as a “cupping” mode, as further detailed below.

The depictions of FIGS. 2A and 3A are generally representative of aperspective circular shape as shown by concentric circles between acenter point and the outer perimeter. Radial lines are also shown, andif the shape were flat such lines would be straight. A curved radialline, however, suggests movement along the line. In this regard,therefore, FIG. 2A is intended to illustrate a first extreme of theoscillatory movement of member MEM, where the surface bends upward(e.g., for reference, in a positive direction) with a maximum peakelevation at the center of the shape (also shown by light gray shading).The upward bend is also appreciated in the counterpart side view of FIG.2B, which shows the mode surface as contrasted to a horizontal, or flat,reference line RL that is shown by a dashed line, and the maximum peakMxP is also indicated. In opposite fashion, FIG. 3A is intended toillustrate a second extreme of the oscillatory movement of member MEM,where the surface bends downward (e.g., for reference, in a negativedirection) also with a peak elevation at the center of the shape (alsoshown by dark gray shading). The downward bend is also appreciated inthe counterpart side view of FIG. 3B, in which the minimum peak MnP isalso indicated.

Given the illustrations of FIGS. 2A, 2B, 3A, and 3B, note that thereference of a mode (0,1) indicates zero (i.e., d=0) nodal diameters anda single (i.e., c=1) nodal circle, the latter shown as D₁. Note that thelocation of the nodal circle will depend on the conditions at theboundary of the membrane, where the illustrations assume that boundaryis claimed; however, if the boundary were not claimed, the radiallocation of the nodal circle will change. In other words, as member MEMoscillates between the extreme positions shown in the Figures, a singlecircle, around the outside perimeter, does not vibrate. The vibrationsinside nodal circle with diameter D₁, therefore, will have some efficacyin removing contaminants that are on the surface of member MEM, but anymatter that lands farther from the center and thus closer to the nodalcircle with diameter D₁ may not experience sufficiently highacceleration to be removed. Further, material in high vibration zonesmay be pushed toward the nodal circles. Still further, and as appreciatelater, a singular mode (0,1) has a limited area on membrane MEM that mayreach a desirable amount of axial acceleration, thereby limiting theability of the membrane to dispel contaminants

By way of an additional example, FIGS. 4A and 5A illustrate perspectiveviews, and FIGS. 4B and 5B illustrate side views, of a membrane MEM andits mode shape diagrams of a second mode (1,1) shape in a standing waveexcitation that may be achieved by applying a first sine wave to twoadjacent segments (e.g., S₁, S₂) of the multiple-segmented transducer14, while simultaneously applying the negative of that sine wave to theremaining two adjacent segments (e.g., S₃, S₄), again therefore whereone applied signal (e.g., sine wave) is 180 degrees out-of-phase withrespect to the other. Note that the second mode (1,1) shape, as well asother standing wave mode shapes, may be achieved in other mannersconsistent with preferred embodiments, and for additional information inthis regard the reader is invited to review U.S. patent application Ser.No. 15/225,212, filed Aug. 1, 2016, which is hereby incorporated fullyherein by reference. The depictions of FIGS. 4A and 5A are againrepresentative of a perspective circular shape as shown by concentriccircles and radial lines, where FIG. 4A is intended to illustrate afirst extreme of the oscillation, and FIG. 5A is intended to illustratea second and opposite extreme of the oscillation. In the first extremeshown in FIG. 4A, and in the counterpart horizontal plot of FIG. 4B,membrane MEM has a maximum peak (i.e., positive) amplitude MxP in afirst region on the right side of a nodal diameter line DL₁, while atthe same time membrane MEM also extends downward below the referenceline RL and has a minimum peak (i.e., negative) amplitude MnP in asecond region on the left side of nodal diameter line DL₁. In the secondextreme shown in FIG. 5A, and in the counterpart horizontal plot of FIG.5B, membrane MEM has a maximum peak MxP on the left side of nodaldiameter line DL₁, while at the same time membrane MEM also extendsdownward below the reference line RL and has a minimum peak amplitudeMnP on the right side of nodal diameter line DL₁. As can be seen inthese Figures, therefore, in mode (1,1) shape for a standing wave,membrane MEM again has a nodal circle around its outer perimeter. Inaddition, however, one diameter line DL₁ represents a nodal line, asoscillations occur left and right of that line, due to the voltageapplied to opposing pairs of conductors/electrodes as introduced justabove (or as achieved in other manners, again, for example withreference to the above-incorporated U.S. patent application Ser. No.15/225,212). Thus, to further illustrate additional aspects below, thealternative oscillations about diameter line DL₁ also may be representedin a top view, as is shown in FIG. 6 , which generally illustrates thetwo separate oscillating regions OR₁ and OR₂, about line DL₁.

By way of one additional example, FIGS. 7A and 8A illustrate perspectiveviews, and FIGS. 7B and 8B illustrate top views, of a membrane MEM andits mode shape diagrams of a third mode (2,1) shape in a standing waveexcitation that may be achieved by applying a first sine wave to twoopposing segments (e.g., S₁, S₃) of the multiple-segmented transducer14, while simultaneously applying the negative of that sine wave to theremaining two opposing segments (e.g., S₂, S₄), again where one appliedsignal (e.g., sine wave) is 180 degrees out-of-phase with respect to theother. One skilled in the art will appreciate from earlier discussionsthat again the depictions of FIGS. 7A and 7B illustrate a first extremeof the oscillation, while FIGS. 8A and 8B illustrate a second andopposing extreme of the oscillation. In the top views of FIGS. 7B and8B, therefore, there are four oscillating regions OR₁ through OR₄, alsomarked with either a “+” indication to designate a positive peak at agiven time or a “−” indication to designate a negative peak at the giventime.

The vibrational mode examples in the above-discussed Figures representthe lowest resonant frequencies of a circular plate system. They arealso the most practical ones because they require the least amount ofenergy needed for excitation. Depending on the drive signal's frequencyand the geometry of the electrodes, the actual vibration pattern can beone of the above-discussed mode shapes or a combination of them. In anycase, they are standing waves. Moreover, having described variousexamples, they also may be characterized mathematically, as to generatea standing wave with the (d, 1) mode when d>0, the circular transduceris divided into 2d channels of equal arc length and inputs are set asshown in the following Equation 1:

S _(2k-1) =S ₀ sin(ω₀ t), S _(2k) =−S ₀ sin(ω₀ t),k=1, . . . , d  Equation 1

where, ω₀ is the resonant frequency of the (d, 1) mode. For the casewhen d=0, only one channel is needed.

FIG. 9 again illustrates transducer 12 in the same general manner asdepicted in FIG. 1B, although in FIG. 9 the illustration is rotated forsake of reference. Further, conductors are shown connected to eachrespective pair of a respective outer electrode SOE_(x) and a segmentinner electrode SIE_(x), and system 10 is also shown to include a drivercircuit 10 _(D) for providing voltage signals to the illustratedconductors, where each voltage output from circuit 10 _(D) is shown astwo signals, so as to suggest the polarity of any signal can bereversed, in order to obtain additional signal and responsive waveoptions, as understood later. Thus, a potential is defined between eachpaired set of conductors. For example, the voltage between outerelectrode SOE₁ and inner electrode SIE₁ is defined as ν_(S1), and notethe (+) and (−) conventions are used to define a polarity for sake ofreference, but as detailed below not to suggest that the outer electrodeis always positive with respect to its inner counterpart. To furtherillustrate this convention, therefore, a voltage of +1V applied toν_(S1) is intended to suggest that the one volt is positive to outerelectrode SOE₁ relative to inner electrode SIE₁, while a voltage of −1Vapplied to ν_(S1) is intended to suggest that the one volt is negativeto outer electrode SOE₁ relative to inner electrode SIE₁. In any event,therefore, driver circuit 10 _(D) may apply any of the illustratedvoltages ν_(S1), ν_(S2), ν_(S3), and ν_(S4). For example, a sine wave ata modal resonant frequency f_(m(1,1)) may be applied to one pair ofconductors/electrodes, with a 180 degree opposite phase sine wave at thesame resonant frequency f_(m(1,1)) applied to an opposing pair ofconductors/electrodes. Thus, in a preferred embodiment, a first phase ofthe sine wave is applied to ν_(S1), while a second phase of the sinewave, 180 degrees apart from the first phase, is applied to ν_(S3); atthe same time, no voltage is applied to ν_(S2) or ν_(S4). Alternativelyto achieve the same mode (1,1), a sine wave at a modal resonantfrequency f_(m(1,1)) may be applied to two adjacent conductors (andtheir respective electrodes), with a 180 degree opposite phase sine waveat the same resonant frequency f_(m(1,1)) applied to an opposing pair ofadjacent conductors (and their respective electrodes). Thus, in apreferred embodiment, a first phase of the sine wave is applied toν_(S1) and ν_(S2), while a second phase of the sine wave, 180 degreesapart from the first phase, is applied to ν_(S3) and ν₄.

It is therefore recognized in connection with the above that certainmodes achievable by transducer 14, if driven with applied voltages tovarious segments will result in symmetric mode shapes. For example the(0,1) shape has a single outer nodal circle with diameter D₁ at itsperimeter, and inside that perimeter the flexing is circularly symmetricas shown by the comparable concentric circles with radii inside thatouter nodal circle, and the greatest amount of displacement is achievedcloser to the membrane center. As another example, the (1,1) shape alsohas an outer nodal circle at its perimeter, but instead of extremeflexing at the center achieved by the (0,1) shape, peaks are achievedoff center but at two different regions; however, a nodal diameter lineis created, along which there is no displacement. As still anotherexample, the (2,1) shape creates peaks off center and at four differentregions; however, two nodal diameter lines are created, along whichthere is no displacement. In all events, therefore, either the drop offin displacement at increased radial lengths of the (0,1) shape, or theadditional nodal diameters of the (1,1) and (2,1) shape, demonstratethat such shapes may be less likely to expel certain contaminants fromlens cover 12 in locations where there is little vibration, that is, itmay tend to accumulate contaminants in nodal circles or diameters. Thepreferred embodiments include additional modes of operation, therefore,so as to achieve improved results over these considerations, as furtherexplored below.

In another aspect of a preferred embodiment, and to overcome thelimitations noted above with respect to contaminants accruing at nodalpoints, circles, or lines, a preferred embodiment further combines bothstanding and traveling waves in system 10, either time multiplexed orconcurrently, as will now be further explored. Specifically, a travelingwave has a wave front that moves as a periodic wave across a surface andtherefore, apart from the outer perimeter of the lens cover and arguablythe center point of the surface around which the wave rotates, has noother stationary point, as compared to various standing waves which, asdemonstrated above, can have one or more points, lines, or circles thatare stationary, despite movement elsewhere on the surface. Moreover, thesame system 10 described above with respect to standing waves also mayreadily be biased, via driver circuit 10 _(D), so as to also achievemechanical traveling waves. By way of introduction, various suchtraveling waves may be achieved by biasing adjacent ones of the foursegments with signals that are 90 degrees apart. The relationship isdescribed mathematically below according to the following Equations 2through 5:

S _(4k-3) =S ₀ sin(ω₀ t)   Equation 2

S _(4k-2) =S ₀ cos(ω₀ t)   Equation 3

S _(4k-1) =S ₀ sin(ω₀ t)   Equation 4

S _(4k) =−S ₀ cos(ω₀ t), k=1, . . . , N   Equation 5

where, ω₀ is the resonant frequency of the [N,1] standing wave.

Implementation of the preceding into system 10 will generate a travelingwave for the (d, 1) mode, whereby the traveling wave front will rotatearound the longitudinal axis 12 _(AX) of the circular lens cover 12 (orother membrane or plate). The direction of rotation can be reversed byreversing the polarity of the inputs in any one set and keeping theother set unchanged. Various implementation details are examples areexplored below.

FIG. 10 illustrates an example mechanical traveling wave graph 20implementing a (1,1) mode traveling wave excitation in system 10 ofFIGS. 1A through 1C, and FIGS. 11 through 14 illustrate the travelingwave rotating around the center axis 12 _(AX) of lens 12. The modedesignations in these examples are for circular traveling waves (d,c)modes having, at an instantaneous point in time where the wave can perperceived as not moving, d nodal diameters and c nodal circles(including the boundary), where d>0 and c>0. In other words, such nodesare points or lines on the lens structure that are momentarily at restin a time instant, but the traveling wave excitation causes the nodes torotate about the lens center axis 12 _(AX). In the example of FIG. 10 ,the traveling wave rotates in a clockwise direction 22 when viewed fromabove and relative to axis 20 _(AX). In this (1,1) mode example,moreover, a single node diameter 24 extends in the indicated X-Y planeabout the Z direction axis 20 _(AX). Thus, FIG. 10 illustrates atraveling wave excitation of a planar lens 12 (not shown in FIG. 10 )that is understood to be positioned in the X-Y plane, and the excitationcauses Z-direction of motion across the lens surface with a positiveZ-direction displacement maxima 26 and a negative Z-directiondisplacement minima 28. FIGS. 11 through 14 provide simplified views ofthe traveling wave rotating in the direction 22 (i.e., clockwise) atdifferent points in time, with FIG. 11 illustrating an initial exampleposition of the maxima 26 and the minima 28 with the intervening singlenode diameter 24 extending in the X direction at Y=0 between thepositive and negative lobes associated with the maximum and minimalpoints 26 and 28. At the time represented in FIG. 12 , the mechanicalvibration by the transducer segments S₁ through S₄ rotates the positionsof the lobes and the points 26 and 28 in the clockwise direction 22 byapproximately 30 degrees. FIGS. 13 and 14 respectively illustratefurther rotation in the direction 22 by additional 30 degree increments,where the node diameter 24 is positioned in the Y-direction in FIG. 14at X=0. In operation, the phase shifted sinusoidal excitation of thetransducer segments S₁ through S₄ causes a continuous rotation of thetraveling wave pattern about the Z-direction lens axis. As seen in FIGS.11 through 14 , the node diameter 24 rotates or travels, in contrast tostanding wave excitation techniques in which the node diameter remainsstationary. Accordingly, the FIG. 9 driver circuit 10 _(D)advantageously provides traveling wave excitation in which the surfacearea of the lens along is vibrated and thus cleaned.

The traveling wave excitation can be mathematically represented. Thedisplacement of a circular lens 12 or other circular plate can berepresented by the following Equation 6:

$\begin{matrix}{{{W_{n,m}\left( {r,\theta} \right)} = {\left\lbrack {{J_{n}\left( {\beta_{nm}r} \right)} - {\frac{J_{n}\left( {\beta_{nm}R} \right)}{I_{n}\left( {\beta_{nm}R} \right)}{I_{n}\left( {\beta_{nm}r} \right)}}} \right\rbrack\begin{bmatrix}{\sin n\theta} \\{\cos n\theta}\end{bmatrix}}},} & {{Equation}6}\end{matrix}$

Where J_(n) is the nth Bessel function, I_(n) is the modified Besselfunction of the first kind, and n and m are mode index numbers, n=0,1,2. . . , m=1,2,3, . . . The natural mode frequencies are given by thefollowing Equation 7:

$\begin{matrix}{\omega_{nm} = {\frac{\lambda_{nm}^{2}}{R^{2}}\sqrt{\frac{D}{\rho T}}}} & {{Equation}7}\end{matrix}$

where R is the radius of the circular plate, T is its thickness, λ_(nm)is a root to Bessel function equations, D is the lens material stiffness(determined by Young's modulus, Poisson's ratio, etc.), and ρ is thelens material density, thereby defining the following Equation 8:

$\begin{matrix}{{R_{n,m}(r)} = \left\lbrack {{J_{n}\left( {\beta_{nm}r} \right)} - {\frac{J_{n}\left( {\beta_{nm}R} \right)}{I_{n}\left( {\beta_{nm}R} \right)}{I_{n}\left( {\beta_{nm}r} \right)}}} \right\rbrack} & {{Equation}8}\end{matrix}$

Equation 6 can be simplified as shown in the following Equation 9:

$\begin{matrix}{{W_{n,m}\left( {r,\theta} \right)} = {{R_{n,m}(r)}\begin{bmatrix}{\sin n\theta} \\{\cos n\theta}\end{bmatrix}}} & {{Equation}9}\end{matrix}$

Solutions for W to a forced response at a resonant frequency ω are givenby the following Equations 10 through 12:

W ₁(r,θ,t)=AR _(n,m)(r)cos nθ cos ωt   Equation 10

W ₂(r,θ,t)=BR _(n,m)(r)sin nθ sin (ωt+α)   Equation 11

W ₃ =W ₁ +W ₂   Equation 12

Rearranging W₃ yields the following Equation 13:

W ₃(r,θ,t)=½ R _(n,m)(r)[(A+B cos α)cos(nθ−ωt)+(A−B cos α)cos(nθ+ωt)+2Bsin α sin nθ cos ωt]  Equation 13

Setting α=0, and A=B, the above can be rewritten as the followingEquation 14:

W ₃(r,θ,t)=AR _(n,m)(r)cos(nθ−ωt)   Equation 14

Equation 14 defines a traveling wave with angular speed ω/n in apositive direction θ. By letting A=−B, the direction is reversed to thenegative θ direction. The transducer segments S₁ through S₄ in thisexample form a circular ring shape so that the light can go through thelens 12 in the center along the direction of the axis 12 _(AX).

From the above, one skilled in the art should appreciate that system 10,providing a transducer 14 with four channels or segments, can providevarious mode shapes for both standing and traveling waves that areimposed on lens 12. Indeed, recall in connection with FIGS. 4A and 5A(and 4B and 5B), that a standing wave (1,1) shape may be actuated bydriver circuit 10 _(D) applying a first sine wave to two adjacentsegments (e.g., S₁, S₂) of the multiple-segmented transducer 14, whilesimultaneously applying the negative of that sine wave to the remainingtwo adjacent segments (e.g., S₃, S₄), again therefore where one appliedsignal (e.g., sine wave) is 180 degrees out-of-phase with respect to theother. Referring to the diagram of FIG. 9 , however, note that likewisea traveling wave (1,1) shape may be actuated by driver circuit 10 _(D)applying 90 degree out of phase signals to each respective segment inthe four segments of the multiple-segmented transducer 14, as shown inthe following Table 1:

TABLE 1 Segment Voltage signal S₁ v_(S1) sin ωt S₂ v_(S2) cos ωt S₃v_(S3) −sin ωt S₄ v_(S4) −cos ωt

In still other preferred embodiments, note that variations may be usedto achieve traveling wave patterns, including, for example, where onlypositive waveforms are available, for instance based on limitations froma signal wave generator. In one such instance, 90 degree phase shiftsbetween adjacent ones of four segments may be achieved by reversingpolarity. Thus, as a first example, FIG. 15 illustrates a preferredembodiment biasing in such an instance, so as to once again achieve atraveling wave (1,1) mode. Hence, in FIG. 16 and contrasting segment S₂to segment S₃, segment S₂ is biased in the positive direction by theconventions of FIG. 9 and with a cosine wave, while segment S₃, isbiased in the negative direction by the conventions of FIG. 9 and with asine wave. Thus, a 90 degree phase shift is achieved as between thesesegments, as further maintained between those segments and the remainingsegments S₁ and S₄ which are biased as also shown in FIG. 15 .Alternatively, in a second example, FIG. 16 illustrates a preferredembodiment biasing that combines with the polling areas of thetransducer segments as oriented so that the directionality of dipoles inone region (e.g., piezoelectric material) align so that when a voltageis applied thereto, the behavior of the dipoles aligned in thatdirection is opposite of that in a second region in which the dipolesare aligned in the opposite direction. FIG. 16 illustrates a preferredembodiment biasing in this latter instance, where the indication of “+”or “−” on a segment is intended to designate the directionality ofdipoles in that segment. Thus, note that the dipoles of segments S₁ andS₃ are reversed, so that while each outer conductor in those twosegments receives the signal sin ωt, the mechanical effect is 180degrees out of phase due to the reversed polling direction of those twodiffering segments. Similar observations can be made with respect to thedipoles of segments S₂ and S₄ as reversed with respect to one another,so that while each outer conductor in those two segments receives thesignal cos ωt, the mechanical effect is 180 degrees out of phase due tothe reversed polling direction of those two differing segments. Lastly,note that additional preferred embodiments may be implemented byextending the four channel concepts described herein to higher modesusing a transducer with more channels (preferably in multiples of foursegments, i.e., 8 segments, 12 segments, and so forth). Further in thisregard, the reader is invited to review co-owned U.S. patent applicationSer. No. 15/186,944, filed Jun. 20, 2016, which is hereby incorporatedfully herein by reference.

FIG. 17 illustrates a preferred embodiment method 30 of operating system10. By way of introduction, method 30 may be controlled driver circuit10 _(D), which can include, or cooperate with, a processor, controller,or other circuit or device, as may be hardwired or programmed byconcepts according to one skilled in the art, and an example of which isshown later in FIG. 18 . As further introduction, such control advancesmethod 30 so as to apply transducer voltages to selective ones (or all)of the conductors/electrodes of system 10, so as to alternate betweendifferent mode shapes created in lens cover 12, via standing andtraveling waves applied to it from transducer 14. In combination,therefore, the standing and traveling waves increase the ability toaccelerate the surface of lens cover 12 so as to achieve a desirablysufficient amount of acceleration coverage across a majority of the areaof the cover. As a result, the accelerated movement of the lens coverincreases the chances of dispelling portions of any contaminants along amajority of the area of the cover. Additional details follow.

Method 30 commences with a start step 32, which may be initiated byvarious apparatus or events, when it is desired to start an attempt toremove particulate from lens cover 12 by vibrating it via transducer 14.For example, where lens cover 12 is part of an automotive application aswas introduced earlier and further explored later, start step 32 may beuser actuated, such as by an operator of the automobile, or a processorcan initiate the step in response to a condition, such as at systemstart-up, or after the passage of time, or response from a sensor orupon detection of some other event, such as rain, that might cause somematter (e.g., water) to come in contact with the exterior of lens cover12. As another example, when lens cover 12 is part of a remote lenssystem (e.g., surveillance camera), step 22 may occur at some fixed timeinterval, or in response to signaling from another device, such as inresponse to environmental conditions or as part of an Internet-of-Thingscommunication. In any event, once step 32 is enabled, method 30 hasbegun, after which method 30 continues from step 32 to step 34.

In step 34, a mode counter md is initialized to a value of one. As willbecome evident below, mode counter md increments, and thereby provides acount, up to a total number of modes TLM that are shaped onto lens cover12, by transducer 14, in cyclic and alternating fashion, so as toattempt to remove contaminants from lens cover 12. Next, method 30continues from step 34 to step 36.

In step 36, voltage is applied to a set of selective ones or all of theelectrodes of transducer 14, via the respective conductors connected tothose electrodes, so as to achieve a mode, indicated as MODE[md],meaning according to the index provided by counter md. Thus, for a firstoccurrence of step 36, a first mode (i.e., MODEM) is effected byapplying the necessary voltage signals to a first set of electrodes soas to accomplish that mode. For example, consider the first mode to bethe application of the mode (0,1) standing shape, discussed earlier inconnection with FIGS. 2A, 3A, 2B, and 3B. To achieve this mode, allouter electrodes SOE_(x) receive a voltage of a first sine wave, whileall inner electrodes SIE_(x) receive a voltage of a second sine wave ofthe same sample amplitude as the first sine wave, but with the two wavesphase offset by 180 degrees; moreover, both sine waves are applied witha frequency f_(m(0,1)), which is the resonant frequency of system 10required to achieve the mode (0,1) shape. Note also that step 36 appliesthe signals to the selected set of conductor/electrodes for a numberindicated as MC cycles, that is, for a duration of input sign wavesequal to MC periods or cycles. The value of MC may be selected byvarious considerations. For example, MC may be based on a pre-programmedvalue or on a feedback signal (e.g., modal resonance frequency whichwill return to a baseline value as contaminant mass is ejected from thesurface), or from information from a camera system from which it can bedetermined if a sufficiently clear image is obtained through the lens.After the MC cycles at the current MODE[md] have been achieved, method30 continues from step 36 to step 38.

In step 38, a condition is evaluated to determine whether the modecounter and has reached a total number of modes TLM that are desired tobe shaped onto lens cover 12, by transducer 14. If and is less than TLM,then method 30 advances from step 38 to step 40, whereas if and equalsTLM, then method 30 advances from step 38 to step 42. In step 40, themode counter and is incremented and the flow returns to step 36. In arepeat of step 36, therefore, an additional set of selective ones or allof the electrodes of transducer 14 receive a voltage so as to achieve anext mode, indicated as MODE[md], which in the case of a firstrepetition of step 26 will be the second mode, that is, MODE[2];however, further in the preferred embodiment, the additional mode may beanother instance of a standing wave, or alternatively it may be atraveling wave. For example, consider the second mode to be theapplication of the mode (1,1) traveling shape, discussed earlier inconnection with FIGS. 10 through 14 . To achieve this mode, recall thatthe signals from Table 1 may be applied, whereby four different phases,across 360 degrees, are applied equally spaced among the four differenttransducer segments. Again, step 36 applies these signals to theselected set of conductor/electrodes for MC cycles, after which method30 again continues from step 36 to step 38.

Step 38 has been described earlier, as it evaluates the condition ofwhether the mode counter and has reached a total number of modes TLMthat are desired to be shaped onto lens cover 12, by transducer 14.Given the sequencing now described, and the potential looping from step38 not being satisfied and returning to step 36 one or more times forthe application of respective additional modes, note that TLM may be setto any number with a corresponding indication of each MODE[md] to beapplied for each incidence of step 36, until the condition of step 38 issatisfied and method 30 continues to step 42.

In step 42, a condition is evaluated to determine whether a sufficientduration of cycles has been applied by the preceding occurrence(s) ofstep 36. To appreciate this step, recall that each incidence of step 36excites transducer 14 to apply either a standing or traveling wave modeshape to lens cover 12, for a total of MC cycles per step 36 incidence.Each of these MC cycles, therefore, endeavors to clear contaminants fromthe surface of lens cover 12. Depending on the number of cycles per step36 incidence, and the number of step 36 occurrences, it may be desirableto repeat the occurrence(s) of step 36 for all TLM modes MODE[md] one ormore additional times, in an ongoing effort to clear contaminants fromthe surface of lens cover 12. Thus, the step 42 condition may useduration (or some other measure) as a basis to evaluate whether torepeat the occurrence(s) of step 36 for all modes MODE[md]. If such arepetition is desired, method 30 returns from step 42 to step 34,whereas if step 42 is satisfied, then method 30 ends in step 44. Whilemethod 30, therefore, concludes with step 44, it may be subsequentlyre-started by returning to step 32, by one of the actions as mentionedearlier with respect to that step.

Given the preceding, one skilled in the art will appreciate that in eachof the multiple different modes, one area of lens cover 12 will achievea maximum or peak acceleration, while various other areas of the lenscover will achieve some lesser percentage of that peak. In an effort toachieve the greatest likelihood of dispelling contaminants, therefore, agreater percentage of peak acceleration across a greater area of lenscover 12 is likely to be desirable. Thus, one criterion to evaluate thecleaning performance is to check the acceleration distribution values onthe lens surface. The acceleration values on the lens surface can becalculated through Finite Element Modeling (FEM) simulation or throughmeasurements from Laser Doppler Vibrometer (LDV). The obtained valuescan then be compared against a prescribed threshold, e.g., 50% of thepeak acceleration value, to determine the lens area that exceeds thethreshold. The area above the chosen threshold will be referred to as‘active area.’ The active area achieved by different excitation methodscan be compared, as is shown in Table 2, which is compares the activearea achieved by (0,1) standing wave, (1,1) traveling wave, and thecombination of the two based on FEM simulation. To simplify thecomparison, the values of the active area as a percentage of the totalarea are listed. Note that the peak value used to calculate thethreshold is the largest value that can be obtained by (0,1) standingwave and (1,1) traveling wave (and in this example, the largest value isachieved by (0,1) standing wave).

TABLE 2 Lens area exceeds threshold (% of lens area) [0, 1] standing and[1, 1] Threshold (% of [0, 1] mode [1, 1] mode traveling wave peakvalue) standing wave traveling wave combined 25% 55.0% 81.3% 84.0% 50%2.6% 30.8% 30.9% 75% 1.1%  6.0% 6.7% 90% 0.5%   0% 0.5%From Table 2, one skilled in the art will appreciate that on average thetraveling wave yields larger active area. However, the largestacceleration value (found in the center of lens 12) comes from thestanding wave excitation. The combination of both excitations yieldsbetter coverage of both center and off-center lens area.

FIG. 18 illustrates ultrasonic lens cleaning system 10 in greaterdetail, including driver circuit (e.g., integrated circuit) 10 _(D) andan even number NS of transducer segments, where in the exampleillustrates NS=4, thereby providing segments S₁ through S₄ to clean alens 12. The illustrated embodiments include an even number NStransducer segments or elements that are mechanically coupled, directlyor indirectly, to the lens 12, where NS is an even integer greater thanor equal to 4. The individual transducer segments S_(x) in this exampleare radially spaced from a center axis 12 _(AX) of the circular lens 12and the electrodes (see, e.g., FIG. 1B) are angularly spaced from oneanother around a periphery of the lens 12. As detailed further below,driver circuit 10 _(D) provides phase shifted oscillating signals AS andAC to the electrodes of the transducer segments S_(x) to generate astanding or mechanical traveling wave to vibrate the lens 12 forimproved ultrasonic cleaning The disclosed driver circuit 10 _(D),system 10, and methods provide improved lens cleaning solutions.

Driver circuit 10 _(D) in this example is a driver integrated circuitpowered by a battery or other power source 104. FIG. 18 shows a cameralens assembly including the ultrasonic lens cleaning system 10. The lensassembly includes the transducer segments S₁ through S₄ forming acylindrical or “ring” configuration which is mechanically coupled tovibrate a lens 12. Lens 12 may be as shown in FIGS. 1A-1C, or may haveother shapes or configurations (e.g., fisheye, single transparentsurface, and the like).

Driver circuit 10 _(D) receives input power from a power supply or powersource 104, such as a battery providing a battery voltage signal VB withrespect to a reference node, such as a ground node GND in one example.Driver circuit 10 _(D) includes a terminal 106 (e.g., an IC pin or pad)to receive the battery voltage signal VB from the power supply 104, aswell as a ground terminal 108 for connection to GND. Driver circuit 10_(D) includes a power management circuit 110 that receives the batteryvoltage signal VB and provides one or more supply voltages (not shown)to power the internal circuitry of driver circuit 10 _(D). In addition,driver circuit 10 _(D) includes terminals 112-1, 112-2, 112-3, . . . ,112-NS and 114-1, 114-2, 114-3, . . . , 114-NS for connection ofmultiplexer signal outputs to the lead wires 142-1, 142-2, 142-3, . . ., 142-NS and 144-1, 144-2, 144-3, . . . , 144-NS to deliver driversignals to the transducer segments 102.

Driver circuit 10 _(D) provides a set of phase shifted oscillatingsignals to cause the transducer segments to vibrate lens 12 tofacilitate or promote cleaning of the lens 12 through provision ofmechanical traveling waves that rotate around the lens axis 12 _(AX). Inone example, driver circuit 10 _(D) provides phase shifted sinusoidalultrasonic drive signals to actuate the transducer segments and causetransducer 14 to mechanically vibrate lens 12 using ultrasonic waves toremove dirt and/or water from the surface of lens 12. Non-sinusoidaloscillating signals can be provided, for example, square waves,pulse-width modulated waveforms, triangular waveforms or other waveformshapes. Mechanical oscillation or motion of lens 12 at ultrasonic wavesof a frequency at or close to the system resonant frequencies canfacilitate energy efficient removal of water, dirt and/or debris fromlens 12. In one example, driver circuit 10 _(D) delivers phase shiftedoscillating drive signals to the transducer segments at or near aresonant frequency of the mechanical assembly. A fixed driver signalfrequency can be used, or the frequency may be adapted by driver circuit10 _(D) to accommodate changes over time or different frequencies can beused for cleaning different types of debris from lens 12. Driver circuit10 _(D) in one example tracks changes in the resonant mechanicalfrequency of an associated lens system, and provides a closed loopsystem to use this information to maintain cleaning performance overtime and in varying environmental conditions.

Driver circuit 10 _(D) includes a signal generator 130 and a phase shiftcircuit 132, along with first and second amplifiers 134-1 (AMP 1) and134-2 (AMP 2) to generate and provide phase shifted oscillating signalsAS and AC to the transducer segments to generate a standing wave across,or a mechanical traveling wave rotating around the center axis 12 _(AX)of, the lens 12. Any suitable amplifier circuitry 134 can be used, forexample, a power op amp circuit designed to accommodate the frequencybandwidth of the signals VS provided by the signal generator 130 and theoutput signal requirements to properly drive a given transducer segment.The signal generator circuit 130 generates a first output signal VS thatoscillates at a non-zero frequency ω. In some examples, the frequency ωis ultrasonic, such as about 20 kHz or more, although not a strictrequirement of all implementations of the presently disclosed examples.In certain examples, the signal generator 130 is an analog circuitcapable of providing an oscillating output signal VS of any suitablewaveform shape in a range of frequencies, for example from 1 kHz through3 MHz, and can provide the signal VS that concurrently includes multiplefrequency components in order to excite the driven transducers atmultiple frequencies concurrently. In one example, the signal generatorcircuit 130 is a pulse width modulated circuit to provide a square waveoutput signal voltage waveform VS. In other examples, the signalgenerator 116 provides sinusoidal output voltage signals. In otherexamples, triangle, saw tooth, or other wave shapes or combinationsthereof can be provided by the signal generator 130.

The phase shift circuit 132 receives the first output signal VS andgenerates a second output signal VC that oscillates at the non-zerofrequency ω. The second output signal VC is phase shifted from the firstoutput signal VS by a non-zero angle. In one example, the signalgenerator circuit 130 generates a sinusoidal first output signal VSrepresented as VS=K*sin(ωt) and the phase shift circuit 132 provides thesecond output signal VC=K*cos(ωt) shifted by 90 degrees from the firstoutput signal VS. The first amplifier 134-1 includes an input to receivethe first output signal VS, and a first amplifier output 136 to generatea first amplified signal AS based on the first output signal VS. Thesecond amplifier 134-2 includes an input to receive the second outputsignal VC, and a second amplifier output 138 to generate a secondamplified signal AC based on the first output signal VC.

Driver circuit 10 _(D) interfaces with the transducer segments byconnection to the IC terminals grouped as driver signal output terminalpairs 112, 114 individually associated with a corresponding one of thetransducer segments 102. The individual driver signal output terminalpairs include a first output terminal 112 that can be coupled to a firstside conductor (e.g., outer side) of a corresponding transducer segment,and a second output terminal 114 that can be coupled to a second sideconductor (e.g., inner side) of the corresponding transducer segment.Driver circuit 10 _(D) may include extra output terminal pairs 112 and114 to allow configuration of the IC to drive different numbers oftransducer segments 102 for different applications, such as NS=2, 4, 8,16, etc. Driver circuit 10 _(D) also includes a routing circuit 140 thatdelivers the first amplified signal AS to a first set of the outputterminals 112, 114 and delivers the second amplified signal AC to asecond set of the output terminals 112, 114 to generate standing wave ora mechanical traveling wave to vibrate lens 12.

The routing circuit 140 can be a fixed interconnection system to routethe signals AS and AC to specific output terminals 112, 114. In otherexamples, a configurable routing circuit 140 can be used to allowreconfiguration of driver circuit 10 _(D) for different applications. Inthe example of FIG. 18 , the routing circuit 140 includes an integernumber NS multiplexers 141-1, 141-2, 141-3, . . . , 141-NS. Theindividual multiplexers 141 corresponding to one of the transducersegments. The individual multiplexers 141 in various examples includetwo or more multiplexer inputs. In the example of FIG. 18 , a firstmultiplexer input of the individual multiplexers 141 is coupled with thefirst amplifier output 136 to receive the signal AS, and a secondmultiplexer input is coupled with the second amplifier output 136 toreceive the second amplified signal AC. The individual multiplexers 141have first and second outputs, including a first multiplexer output 142coupled to deliver a first multiplexer output signal SO to a firstconductor (e.g., outer) side of the corresponding transducer segment102. A second multiplexer output 144 is coupled to deliver a secondmultiplexer output signal SI to a second conductor (e.g., inner) side ofthe corresponding transducer segment. The multiplexers 141-1 through141-NS provide corresponding outer and inner signals SO-1, SO-2, SO-3, .. . , SO-NS and SI-1, SI-2, SI-3, . . . , SI-NS to the respectivetransducer segments 102-1, 102-2, 102-3, . . . , 102-NS as shown in FIG.18 .

A select input of the individual multiplexers 141 receives a selectsignal to select among the inputs. In FIG. 18 , two select inputsreceive select signals P and SC, respectively. In this example, the Pinput signals P-1, P-2, P-3, . . . , P-NS are used to select a polarityfor the corresponding transducer segment and the SC inputs SC-1, SC-2,SC-3, . . . , SC-NS select between the amplified sine signal AS and thephase shifted, amplified cosine signal AC. The individual multiplexers141 operate according to the corresponding received select signals P andSC to provide a selected oscillating signal AS or AC to one of the innerand outer conductors of the corresponding transducer segments. The otherconductor of the associated transducer segment may be coupled to areference voltage, such as the constant voltage signal GND, or to theother oscillating signal.

The routing circuit 140 in FIG. 18 includes a lookup table 126 (LUT) toprovide the select signals P and SC to the multiplexers 141 according toone or more configuration inputs. In certain examples, driver circuit 10_(D) includes at least one configuration input terminal 116, 118 toallow configuration by an external circuit, such as a host circuit 120.Driver circuit 10 _(D) includes four terminals 116 to receive a binarycoded input NS to specify the number of output multiplexers to be usedto drive NS transducer segments. Three input terminals 118 are providedto receive a binary coded ND signal designating the number of nodaldiameters for the resulting traveling wave. The NS inputs provide the NSsignal via lines 122 to the lookup table 126, and the ND inputs providethe ND signal via lines 124 to the lookup table 126.

The LUT 126 in one example is encoded to provide the P and SC signals toconfigure the multiplexers 140 according to the host-specified NS and NDvalues to operate the transducer segments to generate a standing ortraveling wave to clean lens 12. The multiplexers 141 in FIG. 18 allowselection from the sine wave AS or the cosine wave AC based on the P andSC signals from the lookup table 126. In other examples, the individualmultiplexers 141 include a third multiplexer input coupled with areference voltage, such as GND. This configuration allows selectiveinterconnection of specific ones of the outer and/or inner conductorswith the amplified sinewave signal AS, the amplified cosine signal AC orthe reference voltage GND according to the P and SC signals to establisha mechanical traveling wave excitation of lens 12. In this regard,driver circuit 10 _(D) is configurable by the host circuit 120 toimplement a variety of different configurations based on the number oftransducer segments (NS) and the number of nodal diameters (ND). Theconfiguration of the multiplexers 141 provides the polarity and theselection of sine or cosine waveforms for the electrode or electricalconnection of each side of the transducer segments. In the case ofpiezoelectric transducer segments, the segments vibrate when a periodicelectrical signal is applied, in order to separate debris from themechanically coupled lens 12. The entire lens assembly will typicallyhave one or more resonant frequencies determined by the mechanicalproperties of all the components and the boundary conditions, and thesignal generator circuit 130 in certain examples provides the sinewaveVS at a frequency ω at or near one of the resonant points for effective,efficient cleaning

In one example, the lookup table 126 provides the multiplexer selectsignals to configure the polarity (P) and sine/cosine signal (SC)provided by the individual multiplexers 141. The following Table 3 showsan example of these control signals, where AS and AC are sine and cosineamplitude inputs, P and SC are control signal bits. SO and SI are innerand output signal outputs from the multiplexers 141, which aredetermined by the traveling wave pattern to be excited for lenscleaning. This example can be used for a four-segment system such asthose described herein.

TABLE 3 P SC SO SI 0 0 AS GND 1 0 GND AS 0 1 AC GND 1 1 GND AC

One example of the contents of the lookup table 126 is shown in Table 4for a 16-segment system, where NS represents the number of segments andND represents the number of nodal diameters.

TABLE 4 NS ND P SC 16 1 0000 0000 1111 1111 1111 0000 1111 0000 16 20000 1111 0000 1111 0011 0011 0011 0011 16 4 0011 0011 0011 0011 01010101 0101 0101

FIG. 19 illustrates a preferred embodiment vehicle V with system 10implemented in numerous locations relative to the vehicle V. Forexample, a forward facing camera may be installed as part of a system 10in a mount located behind the windshield W of vehicle V. As anotherexample, a respective rearward facing camera may be installed as part ofa system 10 in each of the vehicle side mirror locations SMR, either inaddition to or in lieu of an actual side mirror. As a final example,another rearward facing camera may be installed near or at the rear ofthe vehicle V, so as to assist with backup technology. Each system 10communicates with a processor P, such as a controller, microcontroller,or the like, located either under the hood or inside the interior of thevehicle, where such communication as may be connected by some type ofconductors, including a vehicle network system. In any event, eachsystem 10 is operable to capture light signals as images, for varioustypes of processing and/or display. Moreover, as described above, eachsuch camera has a lens structure (e.g., lens, lens cover), andassociated therewith is a transducer that is operable according tomethod 20 so as to reduce any contaminants on the surface of the lensstructure.

From the above, the preferred embodiments are shown to provide anultrasound lens structure cleaner and architecture method, either as astandalone unit or as part of a larger preferred embodiment system(e.g., a vehicle; surveillance camera; lighting system). Such preferredembodiments provide numerous benefits. For example, greater vibrationcoverage of the lens structure surface is achieved with a combination ofwaves providing both high transverse amplitudes and rotational patterns.As another example, greater acceleration coverage is achieved of thelens structure surface. As still another example, note that strains maybe developed in multiple directions, rather than just the axialdirection, to promote cracking of dried materials. More particularly,besides high transverse acceleration (orthogonal to the surface),lateral strain can be developed, which may be important for crackingdried contaminants Thus, strain may be imposed on the lens surface inboth the radial and tangential directions. Thus, whereas due to thecircular nature of the mode shape, strain is only applied in the radialbut not in the tangential direction, the preferred embodiment may applystrain additionally in the tangential direction, whereby contaminantscan be even more effectively removed. Moreover, asymmetric modes (e.g.,mode (1,1) shape) will apply strain in both directions, leading to moreeffective cracking. As still another benefit, a straightforward drivercircuit may drive system 10. Still further, the preferred embodimentsare implemented without vibration or resonance frequency matchingissues. In view of the above, therefore, the inventive scope is farreaching, and while various alternatives have been provided according tothe disclosed embodiments, still others are contemplated and yet otherscan ascertained by one skilled in the art. Given the preceding,therefore, one skilled in the art should further appreciate that whilesome embodiments have been described in detail, various substitutions,modifications or alterations can be made to the descriptions set forthabove without departing from the inventive scope, as is defined by thefollowing claims.

1. A device, comprising: a signal generator; a phase shift circuitcoupled to the signal generator; a first amplifier coupled to the signalgenerator; a second amplifier coupled to the phase shift circuit; and arouting circuit comprising: a plurality of segment multiplexers, eachcoupled to the first amplifier and the second amplifier, each coupled toa respective pair of output terminals, each respective pair of theoutput terminals coupled to a respective segment of a multi-segmentedtransducer, each segment comprising an outer electrode coupled to afirst terminal of the respective pair of output terminals and an innerelectrode coupled to a second terminal of the respective pair of outputterminals; and a lookup table coupled to each of the plurality ofsegment multiplexers, the lookup table configured to receiveconfiguration signals from an external circuit and to provide selectsignals to the plurality of segment multiplexers.
 2. The device of claim1 wherein the multi-segmented transducer comprises a single body ofpiezoelectric material having a central opening and having an upperannular surface.
 3. The device of claim 1 wherein the lookup table isconfigured to store multiplexer select signals to configure polarity andsine/cosine provided by the plurality of segment multiplexers.
 4. Thedevice of claim 1, wherein the lookup table configured to receive asignal for operation of the plurality of segments of the multi-segmentedtransducer.
 5. The device of claim 1, wherein the routing circuit isreconfigurable.
 6. The device of claim 1 wherein the multi-segmentedtransducer comprises four segments.
 7. The device of claim 1 whereineach segment of a multi-segmented transducer comprises an outerelectrode and an inner electrode.
 8. The device of claim 1, wherein afirst segment in the multi-segmented transducer is adjacent a secondsegment in the multi-segmented transducer.
 9. The device of claim 1:wherein a first segment in the multi-segmented transducer comprises amaterial having first polling in a first direction; and wherein a secondsegment in the multi-segmented transducer comprises a material havingsecond polling in a second direction opposite the first direction.
 10. Amethod, comprising: applying a first voltage to a plurality ofelectrodes of a transducer via respective conductors coupled torespective electrodes of the plurality of electrodes, the first voltageto the plurality of electrodes corresponding to a first mode indicatedby a mode counter; incrementing the mode counter based on whether themode counter is equal to or greater than a threshold number of modes;applying a second voltage to the plurality of electrodes, the secondvoltage corresponding to a second mode indicated by the incremented modecounter, the second mode different from the first mode; and if the modecounter is equal to or greater than the threshold number of modes,resetting the mode counter based on whether a duration of applying thesecond voltage to the plurality of electrodes is less than a thresholdduration of cycles.
 11. The method of claim 10, wherein applying thefirst voltage to the plurality of electrodes comprises: applying avoltage of a first sine wave to a set of outer electrodes; and applyinga voltage of a second sine wave to a set of inner electrodes, wherein asample amplitude of the second sine wave is the same as a sampleamplitude of the first sine wave, wherein the second sine wave is offsetby 180 degrees from the first sine wave.
 12. The method of claim 11,wherein the first sine wave and the second sine wave comprise a samefrequency.
 13. The method of claim 11, wherein applying the voltage ofthe first sine wave comprises producing a standing wave excitation inresponse to the voltage of the first sine wave; and wherein applying thevoltage of the second sine wave comprises producing a travelling waveexcitation in response to the voltage of the second sine wave.
 14. Themethod of claim 10, wherein applying the first voltage to the pluralityof electrodes comprises applying the first voltage to the plurality ofelectrodes for a duration of input sine waves equal to a number ofperiods.
 15. The method of claim 14, wherein the number of periods ispre-programmed.
 16. The method of claim 14, comprising receiving afeedback signal comprising the number of periods for the duration of theinput sine waves.
 17. A method comprising: generating a first outputsignal; phase shifting the first output signal to generate a secondoutput signal, the second output signal shifted by a phase offset fromthe first output signal; routing the first output signal and the secondoutput signal through a routing circuit, the routing circuit comprisinga plurality of segment multiplexers, each of the plurality of segmentmultiplexers receiving the first output signal and the second outputsignal; and providing one of the first output signal or the secondoutput signal to a first conductor of a plurality of conductors of amulti-segmented transducer.
 18. The method of claim 17, wherein routingthe first output signal and the second output signal through the routingcircuit comprises: receiving a select signal to the plurality of segmentmultiplexers.
 19. The method of claim 17, further comprising coupling asecond conductor of the plurality of conductors of the multi-segmentedtransducer to a reference voltage.
 20. The method of claim 17, furthercomprising: coupling a second conductor of the plurality of conductorsof the multi-segmented transducer to the first output signal or thesecond output signal.